Field of the Disclosure
The disclosure relates to a perpendicularly magnetized spin-orbit magnetic device.
Description of Related Art
Magnetic random access memory (MRAM) has advantages of fast speed, low power consumption, high density, non-volatile, and has almost unlimited read and write times, and is predicted as a mainstream of memories coming in the next generation. A main structure of a memory device in the MRAM is a stacked structure formed by stacking a pinned layer of three-layer materials with ferromagnet/non-magnetic metal/ferromagnet, a tunneling barrier layer and a free layer of a magnetic material. Such stacked structure can be referred to as a magnetic tunnel junction (MTJ) device. Since a write current only flows through the selected MTJ device, and magnetic switching is determined by an intensity of the write current and an intensity of an external magnetic field, it avails decreasing the write current after the MTJ device is miniaturized, and effects of simultaneously improving write selectivity and decreasing the write current are theoretically achieved.
The MTJ devices using a spin-orbit-torque (SOT) mechanism to implement read and write operations can be divided into in-plan MTJ devices and perpendicular MTJ devices. Compared to the in-plan MTJ device, the perpendicular MTJ device has a lower operating current, a higher device density and better data storability. A perpendicular spin torque transfer random access memory (pSTT-RAM) is regarded as a memory of the new generation, which records digital information of 0 and 1 through spin transfer switching, and takes the perpendicular MTJ as a main magnetic memory cell structure, which has good thermal stability, and an operating current thereof is smaller compared with that of the other type of the magnetic memory.
If the SOT mechanism is adopted to implement the MRAM structure, an operating speed and write reliability can be further improved. A switching mechanism of the SOT in a perpendicular film plane magnetic torque is to introduce the write current to a heavy metal layer. The heavy metal layer may produce a spin transfer torque (STT) based on a spin Hall effect and the external magnetic field. Moreover, the write current may produce a Rashba torque (RT) after passing through a perpendicular electric field at a material interface and the external magnetic field. Since the STT and the RT are all perpendicular to a direction of the write current and parallel to the film plane, the two torques are added to form the SOT. Therefore, if a magnetic field is applied to the ferromagnetic material on the film plane that is perpendicular to the magnetic torque, the SOT is produced to switch the magnetic torque of the ferromagnetic layer to achieve an effect of writing the memory device. However, the above mechanism requires to additionally input the write current and apply the external magnetic field. Manufacturers hope to simplify design complexity of an operation mechanism used for controlling the magnetic memory cell structure in case that the SOT mechanism is used as a mechanism for reading and writing the magnetic memory cells.